Fine to question it, but the prevailing wisdom (all else being equal) is that carbon has notably better fatigue life than aluminum. This is known well beyond cycling applications (aerospace specifically) and covered well in those areas. A short amount of Google work can go there, and all will typically align with carbon as superior from a fatigue perspective.
This article comes from the one listed below:
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https://www.globalspec.com/reference/30805/203279/html-head-chapter-7-polymer-matrix-composites
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Carbon Fiber vs. Aluminum Bikes: What's Better? | The Pro's Closet
Others mentioning the same fatigue properties: